Science / Weather Glossary

Dry Line: The boundary between the dry desert air mass of the Southwest U.S. and the moist air mass from the Gulf of Mexico. It usually lies north-south across the central and southern High Plains sta . . . View Full Definition

Dry Slot: An area of dry, and usually cloud-free, air that wraps into the southern and eastern sections of a synoptic scale or mesoscale low pressure system. Best seen on a satellite picture, such as . . . View Full Definition

Dusk: The period of waning light from the time of sunset to dark.

Dust: Small particles of earth or other matter suspended in the air. It is reported as 'DU' in an observation and for wide spread dust on the METAR.

Dust Bowl: The term given to the area of the Great Plains including Texas, Oklahoma, Kansas, Colorado, and New Mexico that was most greatly affected during the Great Drought of the 1930's.

Dust Devil: A small, rapidly rotating column of wind, made visible by the dust, dirt or debris it picks up. It usually occurs in arid or semi-arid areas and is most likely to develop on clear, dry, hot . . . View Full Definition

Duststorm: A severe weather condition characterized by strong winds and dust-filled air over a large area. Visibility is reduced to between 5/8ths and 5/16ths statute mile. It is reported as 'DS' in an . . . View Full Definition

Dynamics: A branch of mechanics that deals with forces and their relations to patterns of motion. In metorology, this relates especially to wind and water patterns.

Earthlight (Earthshine): The faint illumination of the dark part of the moon's disk produced by sunlight reflected onto the moon from the earth's surface and atmosphere.

Earthquake: A sudden, transient motion or trembling of the earth's crust, resulting from the waves in the earth caused by faulting of the rocks or by volcanic activity.

Easterlies:

Easterly Wave: An inverted, migratory wave-like disturbance or trough in the tropical region that moves from east to west, generally creating only a shift in winds and rain. The low level convergence and a . . . View Full Definition

Echo: The energy return of a radar signal after it has hit the target.

Eclipse: The obscuring of one celestial body by another.

Ecliptic: The sun's apparent path across the sky that tracks a circle through the celestial sphere.

Ecology: The study of the relationships between living organisms and their environment.

Eddy: A small disturbance of wind in a large wind flow, which can produce turbulent conditions. They can also be areas of warmer air north of the main westerlies or colder air south of the westerl . . . View Full Definition

Electromagnetic Radiation: Also called radiation, it is waves of energy propagated though space or through a material media.

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